Commercially available fluoroelastomers are synthesized by the copolymerization of fluoro olefins, for example ##STR2## Due to the saturated backbone and presence of carbon fluorine bonds, the fluoro polymers have high thermooxidative stability when compared to their hydrocarbon counterparts. The major drawback of these fluoro elastomers is their poor low temperature properties which is reflected in relatively high glass transition temperatures (Tg). The Tg's of oil resistant non-fluorinated elastomers are lower. Nitrile and hydrogenated nitrile rubber exhibit Tg's of about minus 30.degree. C. versus a Tg of minus 20.degree. C. for the fluorinated copolymer described above.
Elastomers derived from the copolymerization of fluorinated olefins with hydrocarbon olefins are also heat resistant due to the saturated backbone in these polymers. However, heat and oil resistance is lower, the lower the fluorine content. Also glass transition temperature of these elastomers is not significantly improved when compared with the corresponding highly fluorinated counterparts.
When a hydrocarbon diene such as 1,3-butadiene bears a fluorinated substituent such as 2-trifluoromethyl, elastomeric homopolymers are obtained. Free radical polymerization can occur in a 1,2; 3,4; or 1,4 manner. Polymerization in the latter mode would lead to backbone unsaturation in the polymer, which is detrimental to the thermooxidative stability of the polymer, more so than the pendant unsaturation generated by polymerization in a 1,2- or 1,4- manner. Elastomeric polymers are also obtained when the hydrogen atoms of 1,3-butadiene are substituted with fluorine atoms (e.g., polyfluoroprene). However, these polymers also suffer from poor thermooxidative instability due to the presence of backbone unsaturation. Thermooxidative stability is increased in polymers derived from highly fluorinated 1,3-dienes, but these materials tend to be plastics.
Highly fluorinated 1,3-dienes can be copolymerized in emulsion with 1,3-diene hydrocarbons. Relatively low Tg materials can thus be obtained. For example, a copolymer of 1,1,2-trifluorobutadiene with butadiene in a 1 to 1 mole ratio has a Tg of minus 48.degree. C.
U.S. Pat. No. 3,308,175 (Barr, Mar. 7, 1967) relates to novel fluorine-substituted dienes, to a method for the preparation thereof, to certain novel intermediates and the preparation thereof, and to certain novel intermediates for the production of homologous fluorine-substituted dienes.
U.S. Pat. No. 3,379,773 (Barr, Apr. 23, 1968) relates to polymeric compositions and to processes for the preparation of those compositions. Copolymers of 1,1,2-trifluorobutadiene-1,3 and the method of preparing the same are described within this reference along with comonomers hexafluorobutadiene-1,3; 3,4-dichloro-3,4,4-trifluorobutene-1; 2,2,2-trifluoroethyl vinyl ether; vinyl chloride; styrene; 1,1,2-trifluorobutene-1; and 1,1,4,4-tetrafluorobutadiene-1,3.
U.S. Pat. No. 3,398,128 (Bolstad et al, Aug. 20, 1968) relates to halogen-containing copolymers of 1,1,2-trifluorobutadiene-1,3 and another fluorinated 1,3-diene having from 4 to 5 carbon atoms per molecule containing two fluorine atoms on a terminal carbon atom and at least one hydrogen atom and the process for copolymerization of those monomers to produce such copolymers.
U.S. Pat. No. 3,562,341 (Tarrant et al, Feb. 9, 1971) relates to incompletely polyfluorinated 1,3-dienes capable of forming crosslinked polymers and having fluorine substituents in at least the 1,1,2-position, and to synthesis for their preparation. More particularly, this reference relates to a synthesis for 1,1,2-trifluorobutadiene-1,3 and to the compounds 1,1,2,4,4-pentafluorobutadiene-1,3, and 1,1,2,4,4-pentafluoro-3-methylbutadiene-1,3.
U.S. Pat. No. 3,607,850 (Smith, Sept. 21, 1971) relates to a method of polymerizing conjugated fluorinated dienes which are rubber-like, flexible at low temperatures, and resistant to mineral oils and other chemicals. More particularly, the reference relates to use of rhodium salts or complexes as catalysts for the polymerization or copolymerization of conjugated fluorinated dienes to produce high molecular weight elastomers.